Method and apparatus to monitor the compressive strength of insulation boards

ABSTRACT

A method for producing foam insulation board, the method comprising forming a foam product as part of a continuous process, and monitoring on-line the compressive strength of the foam product.

This application claims priority from U.S. Provisional Application No.60/497,675, now abandoned, filed in Aug. 25, 2003, now abandoned, and ishereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a method and apparatus to monitor thecompressive strength of insulation boards along their trimmed edgesduring manufacture of the boards.

BACKGROUND OF THE INVENTION

Polyurethane and polyisocyanurate foam insulation boards are commonlyemployed in the construction industry. These insulation boards aregenerally cellular in nature and typically include an insulatingcompound trapped within the cells of the foam.

The physical characteristics of the board are important to the overallperformance of the board. For example, dimensional stability isimportant because insulation boards are exposed to a full range ofweather. Where insulation boards are employed to insulate flat orlow-slope roofs, shrinkage of these insulation boards from coldtemperatures can cause a loss of insulating efficiency. In particular,when the dimensional stability of the foam matrix is low, the edges(especially the 8′ edges of, for example, standard 4′×8′ boards) aresusceptible to edge collapse during exposure to cold temperatures. Thiscollapse can cause the top facers and bottom facers along these edges tobend towards each other.

As a result, it is common in the industry to test insulation boards forcold-age dimensional stability (ASTM D2126). Alternatively, thedimensional stability of insulation boards, primarily the edges, can bedetermined by analyzing the perpendicular compressive strength of theseedges (i.e. the compressive strength in the cross-machine direction).The higher the perpendicular compressive strength of the insulationboards along these edges, the better the cold age dimensional stabilityof the insulation boards.

The dimensional stability of insulation boards is believed to beimpacted, especially near the edges of the board, by the degree ofpolyurethane crosslinking (isocyanurate formation). Incompletecrosslinking tends to be a problem near the edges of the board becauseless heat is present at the edges following manufacture of the boards.In other words, the boards are typically stacked or bundled followingmanufacture, and the heat that is generated and trapped within theboards tends to drive crosslinking; the exposed surface area around theedges of the stacks or bundles allows the edges to cool more rapidlywhich results in decreased crosslinking.

Also, the dimensional stability of insulation boards is believed to beimpacted, especially near the edges of the board, by the shape andorientation of the cells within the foam. Particularly, it is believedthat if the cells of the foam matrix are spherically-shaped, instead ofbeing egg-shaped, then the dimensional stability of the roofing board isrelatively high; but if the cells are egg-shaped, then the dimensionalstability of the roofing board is relatively low along at least one ofthe three major axes. For example, if the major (as opposed to minor)axes of the egg-shaped cells are aligned parallel to the rise directionof the foam (i.e. perpendicular to the facers), then the dimensionalstability perpendicular to the rise direction will be relatively low.

Several solutions have been suggested in the prior art and/or arepracticed commercially to improve the dimensional stability of theinsulation boards, particularly along edges. These solutions primarilyinvolve adjusting manufacturing parameters. These parameters include,but are not limited to, manufacturing techniques, conditions,ingredients, and ingredient amounts. Thus, one could use compressivestrength analysis to glean dimensional stability and alter thesemanufacturing parameters to produce an insulation board having atechnologically useful dimensional stability.

But, the problem encountered derives from the fact that insulationboards are commercially produced in a continuous operation. Thesecontinuous manufacturing processes can suffer from quality controlissues—particularly related to dimensional stability along the edgesbecause adjustments to these processing parameters are best made duringthe process. Heretofore in the art, these adjustments to the processingparameters were made only after an insulation board was removed from theprocess, analyzed for compressive strength, and the data from this testwas provided to an operator who could then make the appropriateadjustments. Not only is the removal of the board from the manufacturingprocess labor intensive, but depending upon the frequency of the qualitycontrol tests, hundreds of feet of insulation board could bemanufactured before appropriate adjustments could be made to correct forquality control issues.

There is therefore a need to improve the manufacturing process ofinsulation boards such that quality control, particularly dimensionalstability, can be improved.

SUMMARY OF THE INVENTION

The present invention provides a method for producing foam insulationboard, the method comprising forming a foam product as part of acontinuous process, and monitoring on-line the compressive strength ofthe foam product.

The present invention also provides an edge-strength measuring devicefor measuring the compressive strength of a foam matrix along the edgesthereof, the device comprising at least one measuring implement havingone or more contacting elements for engaging with the edges of the foammatrix, and at least one measuring device in communication with saidcontacting elements for measuring the resistance imparted by the foammatrix when said contacting element is engaged with the edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective cross-sectional view of aninsulation board.

FIG. 2 is a side elevational view of a preferred apparatus for thecontinuous production of the insulation board.

FIG. 3 is a fragmentary schematic view of the second half of themanufacturing apparatus used to produce the insulation board.

FIG. 4 is a fragmentary elevational view from the rear of one embodimentof an edge-strength measuring device employed in the present invention.

FIG. 5 is a fragmentary enlarged plan view of a measuring implementemployed in the edge-strength measuring device depicted in FIG. 5.

FIG. 6 is a fragmentary plan view of another embodiment of anedge-strength-measuring device employed in the present invention.

FIG. 7 is a fragmentary elevational view from the rear of theedge-strength measuring device depicted in FIG. 6.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention includes a process whereby insulation boards aremanufactured and the compressive strength along the edges of the foamproduct is monitored on-line as part of the manufacturing process. Inone preferred embodiment, the compressive strength is monitoredcontinuously throughout the manufacturing process. By having continuousreal-time compressive strength data, an operator can adjust themanufacturing process to ensure the proper quality of the insulationboards.

The insulation boards that are produced include those that areconventional in the art except for their improved quality or consistencyas a result of the advantages offered by practicing the presentinvention. Preferred boards include those having a polyurethane orpolyisocyanurate foam core. Polyurethane and polyisocyanurate foams areproduced in a continuous manufacturing process by contacting an“isocyanate component” with a “polyol component.” The “isocyanatecomponent” generally includes an isocyanate or polyurethane prepolymer.“Polyol component” generally includes a polyol and/or glycol, and,usually, small amounts of water, but “polyol component” refers to anyisocyanate-reactive component as generally known in the art, including,for example, noon-limiting example, diols, glycols, polyols, water, andprimary and secondary amines. A blowing agent is typically dissolved inor emulsified in the polyol component. The isocyanate and polyolcomponents are contacted and dispensed onto a moving form, where theyreact and produce heat. The evolving heat and the chemical reactionstaking place serve, together with other factors such as frothing,generally cause formation of a cellular foam product. It is believedthat the heat causes the blowing agents, such as pentanes, which areadded as liquids, to volatize and form gas that becomes suspended in thereaction mixture to produce a cellular foam. Water, added purposefullyor as part of the polyol component, reacts with isocyanate to producecarbon dioxide (CO₂), which is also suspended in the reaction mixture toproduce a foam. The isocyanate component is typically delivered to themanufacturing process as part of an “A-side” stream of reagents and thepolyol component is typically delivered as part of a “B-side” stream ofreagents. Processes for the manufacture of polyurethane andpolyisocyanurate foam insulation boards, as well as the ingredients anduseful amounts thereof, are generally known in the art as described inU.S. Patent Application Publication No. 2004/0082676, which isincorporated herein by reference.

FIG. 1 shows a foam product 10, which includes a foam matrix 11 having afirst major surface 12 and second major surface 13. An optional firstfacer material 14 and an optional second facer material 15 mate withfirst major surface 12 and second major surface 13, respectively. Foamproduct 10 includes first side edge 58 and second side edge 59. Theseedges continue along the entire length of foam product 10 (i.e.,parallel to the longitudinal or machine direction of matrix 11) and areadjacent to the side plates of the laminator (not shown). These edgesare perpendicular to the plane formed by facers 14 and 15, and may alsobe referred to as rise edges. Unless specifically distinguished herein,reference to edges refers to these side edges 58 and 59.

Foam product 10 preferably has a thickness from about 1 to about 4inches, and during at least a portion of the production process, thelength of the foam product is continuous so long as reactants areavailable to form the foam product. Although not specifically shown,foam product 10 is ultimately sized to desired dimensions depending onthe intended application. For example, foam product 10 can be trimmed toa width of 4 feet and cut to length of 8 feet to form a 4′×8′ insulationboard, which size is often useful in the building trades.

Foam matrix 11 can be polyisocyanurate foam, polyurethane foam, ormixtures thereof. Foam matrix 11 is generally of standard production,and generally includes those having an index of about 250. Particularly,when polyisocyanurate foam is employed, those having an index above 200are preferred; and when polyurethane foam is employed, an index above120 is preferred. Nominal density of the polyisocyanurate orpolyurethane foam is about 2 pounds per cubic foot (pcf).

First facer material 14 and second facer material 15 can comprise apolymer material, a reinforced polymer material, or a reinforcedcellulosic material, as well as paper, aluminum foil and trilaminatesthereof. The polymer material can include polypropylene, polymerlatexes, polyamides, or mixtures thereof, and the cellulosic materialcan include recycled paper, cardboard, and the like.

Thicknesses of the facers typically range between about 0.01 and 0.15inches. An exemplary polyamide facer material includes polyamide 6,6although other polyamides are equally suitable. The thickness of apolyamide facer of the present invention ranges from about 0.25 mils toabout 10 mils, preferably from about 0.4 mils to about 8 mils, and mostpreferably from about 0.5 mils to about 6 mils.

While practice of this invention does not generally alter theconventional methods that are used to continuously produce insulationboards, it is believed that the invention is best described bydescribing the overall manufacturing process. A typical continuousprocess for the manufacture of insulation boards is depicted in FIGS. 2and 3 in conjunction with a first apparatus portion 20 (FIG. 2) and asecond apparatus portion 50 (FIG. 3).

As shown in FIG. 2, the first apparatus portion 20 includes a laminatorassembly 22. Laminator assembly 22 includes a continuous upper belt 24and a continuous lower belt 25, which are both reeved around a series ofrollers 26. Several of the rollers 26 are preferably driven and providefor the movement of first facer material 14 and second facer material15. For example, second facer material 15 is initially carried by aspool 28, and is thereafter fed into position in laminator assembly 22by continuous upper belt 24.

A foam mixhead 30 is positioned immediately above first facer material14 as it enters laminator assembly 22. Foam ingredients (i.e., theA-side and B-side reagents) are delivered from reservoirs 31 and 32, fedthrough metering pumps 33 and 34, and through appropriate conduits 35into a mixhead 30, where upon contact with one another, a reactioncommences to form foam matrix 11.

Mixhead 30 supplies an appropriate mixture 36 of foam ingredients fromthe reservoirs 31 and 32, as well as an appropriately metered amountthereof, onto the surface of first facer material 14. Subsequently, andslightly downstream of foam mixhead 30, second facer material 15 is fedinto laminator assembly 22 from spool 28. Before contacting mixture 36,second facer material 15 passes around a feed roller 38 that positionssecond facer material 15 against upper belt 24. As lower facer material14, upper facer material 15, and mixture 36 are conveyed, mixture 36rises, as depicted at 40, until second facer 15 is in complete contactwith upper belt 24. Upper belt 24 and lower belt 25 are adjustable toaccommodate the desired thicknesses of matrix 11.

After the foaming of mixture 36 has completed, an intermediate foamproduct 42 (FIG. 2) may be heated to effect curing. For example,intermediate foam product 42 can be passed through ovens or heaters (notshown). After curing for the appropriate time and temperature,continuous foam product 10 emerges from first apparatus portion 20 andis directed toward second apparatus portion 50 by a conveyer 46.

As discussed above, the advantageous monitoring of the present inventionpreferably occurs once foam product 10 passes through first apparatusportion 20. On-line monitoring of the compressive strength refers to thefact that the compressive strength is measured without removing thecontinuous product 10 (or the resultant insulation boards 10′ shown inFIG. 3) from the production line during the manufacturing process.Indeed, monitoring occurs while the continuous product 10 or insulationboards 10′ travel along the conveyer 46 during the manufacturingprocess. While the monitoring of the compressive strength is preferablycontinuous, which refers to the fact that the monitoring persiststhrough the manufacturing process, the monitoring can be performedintermittently or in intervals as the manufacturing process warrants.For example, monitoring can occur at every other 8′ length of matrix 11or foam product 10, or monitoring can occur at intervals, for example an8′ length within a larger segment of foam product 10, such as a 100′length.

A preferred apparatus for conducting on-line monitoring is describedwith reference to FIG. 3. For example, as seen in FIG. 3, secondapparatus portion 50 includes a trimming implement 51, an edge-strengthmeasuring device 52, an optional perforation implement 53, and a sawingimplement 54. Foam product 10 is directed through second apparatusportion 50 by conveyer 46 having rollers generally indicated by thenumeral 48 in FIGS. 2 and 3. Foam product 10 emerges from secondapparatus portion 50 as insulation board 10′. The position within secondapparatus portion 50 at which the on-line monitoring occurs is notcritical. In fact, on-line monitoring may take place before or after thetrimming step, before or after the optional perforation step, or beforeor after the cutting step. With this understanding, further reference toon-line monitoring will be made with respect to foam matrix 11, whichmay be included in either continuous product 10 or board 10′.

Trimming implement 51 is used in a trimming operation to trim to sizecontinuous product 10 or board 10′ in the direction that conveyer 46 ismoving (i.e. the so-called machine direction). That is, trimmingimplement 51 is provided to trim the edges of continuous product 10 orboard 10′ aligned in the machine direction to provide trimmed edgestrimmed edges 58 and 59, which are shown in FIG. 1, and which arepreferably parallel to one another. The distance between the trimmededges 58 and 59 provides the width of boards 10′. For example, if boards10′ are sized to be 4′×8′, the distance between trimmed edges 58 and 59would likely be 4′.

Although edge-strength measuring device 52 can be positioned before orafter the trimming implement 51, the trimming operation is preferablyperformed before foam product 10 or board 10′ enters edge-strengthmeasuring device 52. Advantageously, when edge-strength measuring device52 interfaces with flat or trimmed edges, edge-strength measuring device52 provides relatively more consistent measurements. Accordingly,trimmed edges 58 and 59 are preferably formed (via trimming) on thecontinuous product 10 or board 10′ before the compressive strength ofthe foam matrix 11 is measured.

Perforation implement 53 is preferably used to provide proper laminationof first facer material 14 and second facer material 15 to foam matrix11, and to facilitate application of hot asphalt to the insulatedroofing boards by releasing unwanted gases such as moisture vaporgenerated during the manufacturing process or other gases associatedwith first facer material 14 and second facer material 15. Perforationimplement 53 preferably includes a plurality of needles (not shown)arranged on either side of board 10′. The needles are used to perforatefirst facer material 14 and second facer material 15 to release pocketsof unwanted gases, and to simultaneously drive portions of first facermaterial 14 and second facer material 15 into foam matrix 11. As such,the portions of first facer material 14 and second facer material 15driven into foam matrix 11 are effectively interlocked with foam matrix11.

Sawing implement 54 is used to cut continuous foam product 10 intoboards 10′ of desired length. As such, product 10 is cut in a directionperpendicular to the machine direction to provide foam boards 10′.Preferably, the step of sawing occurs after the step of trimming.

In a preferred embodiment, the compressive strength of the matrix 11along trimmed edges 58 and 59 is continuously measured by employing theedge-strength measuring device 52. The preferred apparatus produces asignal representing the force imparted on the apparatus when engagedwith trimmed edges 58 and 59. The signal is preferably calibrated toaccount for the area of contact between a contacting implement ofedge-strength measuring device 52 and trimmed edges 58 and 59 to producea pressure measurement. This pressure measurement can be related ortranslated to the compressive strength of foam matrix 11 along trimmededges 58 and 59 thereof, and can be used by an operator to adjust themanufacturing process to provide necessary compressive strengthaccording to specified tolerances.

The edge-strength measuring device 52 is shown in FIGS. 4 and 5.Edge-strength measuring device 52 includes two portions positionedadjacent the sides of the conveyer 46. Each of these two portions employa measuring implement 70 positioned proximate to matrix 11 and orientedin the cross-machine direction to interface or engage with one oftrimmed edges 58 and 59. Measuring implements 70 are likewise preferablypositioned in opposed relation to one another. Preferably, the opposedmeasuring implements 70 are mirror images of one another and are alignedin the cross-machine direction on opposite sides of the continuousproduct 10 or boards 10′. For illustrative purposes, only half ofedge-strength measuring device 52, including one of the opposedmeasuring implements, is shown in FIGS. 4 and 5.

Measuring implement 70 depicted in FIGS. 4 and 5 is disposed proximatethe trimmed edge 59, and is supported by a stationary table 72 havinglegs 73 and braces 74 extending between the legs 73. A support post 76extends upwardly from the stationary table 72 to support an upper brace78 and an extension bracket 80. Extension bracket 80 supports aself-adjusting assembly 82. Braces 74 and upper brace 78 extend betweenthe two opposed portions of the edge-strength measuring device 52 toprovide a rigid interconnection therebetween.

Self-adjusting assembly 82 provides for the positioning of measuringimplement 70, and includes a vertically-oriented linear slide 84 and ahorizontally-oriented linear slide 86. Vertically-oriented linear slide84 is attached to extension bracket 80 and includes a sliding member 88.Sliding member 88 is capable of moving vertically up and down, andconnects the remainder of self-adjusting assembly 82 with extensionbracket 80. As such, vertically-oriented linear slide 84 is capable ofvertically repositioning measuring implement 70, and the remainder ofself-adjusting assembly 82 (including horizontally-oriented linear slide86).

As shown in FIG. 4, an L-shaped shelf 90 is attached to the slidingmember 88 to connect horizontally-oriented linear slide 86 with slidingmember 88. More specifically, L-shaped shelf 90 includes a firstvertical member 92 attached to sliding member 88, and a secondhorizontal member 93. Second horizontal member 93 supportshorizontally-oriented linear slide 86, which is capable of moving in andout relative to first vertical member 92. For example,horizontally-oriented linear slide 86 is capable of sliding onhorizontal slide members 94 (both of which are shown in FIG. 5).Horizontal slide members 94 are parallel to one another, and serve astracks for guiding horizontally-oriented linear slide 86.Horizontally-oriented linear slide 86, which is guided by horizontalslide members 94, is therefore capable of horizontally repositioning (inthe cross-machine direction) measuring implement 70.

Positioning sensors such as photo-electric and ultrasonic sensors arepreferably used to properly position the measuring implements 70relative to trimmed edges 58 and 59. For example, first and secondphoto-electric cells 130 and 131 produce signals relating to theposition of the matrix 11; these signals are preferably relayed to acomputer microprocessor (not shown), which is attached tovertically-oriented linear slide 84 and horizontally-oriented linearslide 86. The computer microprocessor is capable actuatingvertically-oriented linear slide 84 and horizontally-oriented linearslide 86 according to the signal to position measuring implements 70 sothat they contact trimmed edges 58 and 59.

Self-adjusting assembly 82 also includes a vertically extendingattachment plate 96 attached to horizontally-oriented linear slide 86 tosupport measuring implement 70 relative to horizontally-oriented linearslide 86. Attachment plate 96 supports an L-shaped supporting member 100that includes a horizontal portion 102 and a vertical portion 103. Asshown in FIGS. 4 and 5, horizontal portion 102 extends outwardly fromattachment plate 96 over horizontally-oriented linear slide 86 andmeasuring implement 70 is attached to the vertical portion 103.

Measuring implement 70 includes a proving ring 106 having integrallyattached first and second bosses 108 and 109. As shown in FIGS. 4 and 5,first boss 108 is attached to vertical portion 103 of the L-shapedsupporting member 100, and second boss 109 is attached to a contouredbracket 110. Contoured bracket 110 is also part of measuring implement70 and supports a contacting element 112 (i.e. a sphere, ball, cylinder,or the like), which is used to contact the matrix 11 of board 10. Forexample, as shown in FIGS. 4 and 5, the contacting element 112 is asphere. The sphere employed as the contacting element 112 is attached tothe contoured bracket 110 by a pin 114, and is able to rotate about theaxis of the pin using various bearings (not shown).

When the measuring implements are properly positioned proximate totrimmed edges 58 and 59, contacting elements 112 interface with trimmededges 58 and 59. To that end, the sphere, ball, cylinder, or the likeare preferably made of materials that have limited adhesion with (andhence generate little friction when contacting) foam matrix 11 as thecontinuous product 10′ or boards 10 are passing through device 52. Forexample, the sphere, ball, cylinder, or the like can be composed of aplastic material such as PVC or polyurethane, or can be composed of ametallic material such aluminum coated with a low-friction coating suchas a fluoro-coating like Teflon™.

Contacting element 112 extends partially through an aperture (not shown)of a sled 120. Sled 120 is attached to attachment plate 96 (and theself-adjusting assembly 82) via a sled support post 121. Sled 120 isused to position contacting element 112 relative to foam matrix 11. Forexample, because continuous product 10 or boards 10′ travel in themachine direction (from the bottom to the top of FIG. 5), sled 120includes a non-slanted portion 122 (through which the above-discussedaperture is provided), a slanted portion 124, and optionally a secondslanted portion 125. During operation of edge-strength measuring device52, slanted portion 124 is used to funnel matrix 11 into position alongnon-slanted portion 122. When the matrix 11 is properly positionedrelative non-slanted portion 122, contacting element 112, which extendspartially through the aperture, contacts trimmed edge 59 (FIG. 4).Therefore, as trimmed edge 59 passes along sled 120, slanted portion 124ensures proper positioning of matrix 11 with respect to non-slantedportion 122 and sphere 112.

With reference to FIG. 4, sled 120 is also preferably provided withfirst and second photo-electric cells 130 and 131, which serve as theabove-discussed position sensors. First and second photo-electric cells130 and 131 are respectively positioned using first and second brackets132 and 133, which are opposed to one another proximate one end of sled120. As such, as matrix 11 of continuous product 10 or boards 10′ passthrough device 52, matrix 11 passes between first and secondphoto-electric cells 130 and 131.

First and second photo-electric cells 130 and 131 are provided tomeasure the position of matrix 11 relative to contacting element 112. Tothat end, first and second photo-electric cells 130 and 131 providesignals proportional to the distance between themselves and, whenappropriate, first major surface 12 or first facer material 14 andsecond major surface 13 or second facer material 15. A computermicroprocessor can process these signals to determine whether measuringimplements 70 are properly positioned relative to matrix 11. Othersensing devices can be employed such as ultrasonic sensors. As thoseskilled in the art appreciate, the use ultrasonic sensors obviate theneed for sensing devices above and below matrix 11. Also, the process ofthis invention can be operated without sensing devices provide that thewidth of matrix 11 is known and provided that the position of matrix isfixed with respect to the conveyor 46.

Depending on the signals received from first and second photo-electriccells 130 and 131, a computer microprocessor can control the actuationof vertically-oriented linear slide 84 and horizontally-oriented linearslide 86 to position contacting element 112 such that it contacts foammatrix 11. In doing so, the computer microprocessor actuatesvertically-oriented linear slide 84 and horizontally-oriented linearslide 86 to position contacting element 112 in the vertical center ofthe trimmed edge 59. First and second photo-electronic cells 130 and131, and the control provided by the computer microprocessor, are usedto maintain the proper position of contacting elements 112 relative totrimmed edges 58 and 59.

When contacting element 112 is properly positioned with respect totrimmed edge 59, for example, contacting element 112 presses into foammatrix 11 along trimmed edge 59, and foam matrix 11 resultantly exerts aforce against the element 112. The positioning of contacting element 112is preferably fixed with respect to sled 120. As a result, sled 120 iseffectively pressed against trimmed edge 59 and contacting element 112is positioned such that, as it is pressed into foam matrix 11, it ismaintained at a constant depth. Preferably, the area of the impressionis constantly maintained by the proper positioning of the measuringimplement 70 (especially contacting element 112 and sled 120) by thecomputer microprocessor. Consequently, the outline of the impression or“footprint” of contacting element 112 will be constant as matrix 11passes along conveyer 46 past measuring implement 70.

Proving ring 106 is adapted to measure the force exerted by foam matrix11 on contacting element 112 and generate a signal that can be forwardedto the computer microprocessor. For example, the force exerted by foammatrix 11 is imparted through contacting element 112, contoured bracket110, and second boss 109 to ring portion 140 of proving ring 106.Because proving ring 106 is exposed to the imparted force, ring portion140 deforms in relation to the imparted force. That is, proving ring 106is adapted to deform according to force imparted by foam matrix 11 oncontacting element 112.

Ring portion 140 is preferably provided with a “linear variabledifferential transducer” (LVDT) 142 and an armature 143 to accuratelymeasure the amount of imparted force. Armature 143 interacts with LVDT142 to generate a signal proportional to the deformation of ring portion140 and, hence, the imparted force. LVDT 142 and armature 143 areaffixed on the interior of ring portion 140. For example, as seen inFIG. 5, armature 143 is affixed adjacent first boss 108, and LVDT 142 isaffixed adjacent to second boss 109.

LVDT 142 includes a cylinder (or tube) and armature 143 is adapted topartially fit inside LVDT 142. A voltage is induced in LVDT 142, whichvaries according to the displacement of the armature 143 relative toLVDT 142, in order to generate a signal proportional to the impartedforce. For example, armature 143, is preferably configured to be capableof moving 0.03″ relative to LVDT 142, and using the induced voltage,LVDT 142 generates a signal that is linearly proportional todisplacement (from 0.00 to 0.03″) of armature 143 inside LVDT 142.Therefore, when ring portion 140 is deformed, armature 143 is displacedinside LVDT 142, and an appropriate signal is generated. Because thereis a direct relationship between the imparted force, the deformation ofring portion 140, and the displacement of armature 143 inside LVDT 142,this signal is directly related to the magnitude of the imparted force.

The signal generated by LVDT 142 is relayed to the computermicroprocessor, which modifies the signal according to the area of thefootprint of contacting element 112 (as described hereinabove). Thecomputer microprocessor is calibrated according to the area of thefootprint to generate a pressure measurement indicating the compressivestrength along, for example, trimmed edge 59. That is, the computermicroprocessor converts the signals generated by LVDT 142 into qualitycontrol information (i.e., the pressure measurement) indicating thecompressive strength along the edges of the foam matrix.

A second embodiment of the edge-strength measuring device is generallyindicated by the numeral 152 in FIGS. 6 and 7, and, like the firstembodiment (edge-strength measuring device 52), includes two portionspositioned adjacent the sides of conveyer 48. Each of these two portionsinclude a measuring implement 160 positioned proximate to matrix 11 tointerface with trimmed edges 58 and 59 thereof. Like the two portions ofedge-strength measuring device 52, the measuring implements 160 ofedge-strength measuring device 152 are also positioned in opposedrelation to one another aligned in the cross-machine direction onopposite sides of matrix 11. That is, the measuring implements 160 aremirror images of one another, and, consequently, for illustrativepurposes, only half of edge-strength measuring device 152 including onemeasuring implement 160 is shown in FIGS. 6 and 7.

Measuring implement 160 depicted in FIGS. 6 and 7 is disposed proximatetrimmed edge 58 on the left of conveyer 46 in the machine direction. Tosupport measuring implement 160, edge-strength measuring device 152includes a stationary table 162 including a support plate 163 and legs164 extending downwardly from support plate 163. Braces 165 attached tolegs 164 extend between the two portions of the edge-strength measuringdevice 152 underneath conveyer 46 to provide a rigid connectiontherebetween.

A self-adjusting assembly 166 is attached to support plate 163, andincludes vertically-oriented linear slide 168, a vertical slide member169 actuated by vertically-oriented linear slide 168, a platform bracket172, a rail member 173, a horizontally-oriented linear slide 174slidable on rail member 173, and first and second horizontal slidemembers 176 and 177.

As shown in FIG. 7, vertically-oriented linear slide 168 extendsdownwardly from support plate 163, and is positioned between legs 164.Vertical slide member 169 extends upwardly from vertically orientedlinear slide 68 through an aperture (not shown) in support plate 163.Vertical slide member 169 is capable of vertical movement up and downvia actuation of vertically-oriented linear slide 168.

Platform bracket 172 is attached to upper extremity of vertical slide172, and supports of rail member 173. Horizontally-oriented linear slide174 is slidable on rail member 173 in a direction perpendicular to themovement of continuous product 10′ or board 10 on conveyer 46. As such,horizontally-oriented linear slide 174 can be roughly adjusted relativetrimmed edge 58, and, as discussed below, first and second horizontalslide members 176 and 177 can be finely adjusted relative trimmed edge58 to position measuring implement 160 proximate in proximity thereto.

First and second horizontal slide members 176 and 177 are positioned onopposite sides of horizontally-oriented linear slide 174, and arecapable of reciprocal motion in the cross-machine direction. That is,first and second horizontal slide members 176 and 176 are capable ofhorizontal movement in and out relative trimmed edge 58 via actuation ofhorizontally-oriented linear slide 174. As such, the proper position ofa contacting element 180 (i.e. a sphere, ball, cylinder, or the likeused in the measuring implement 160) relative trimmed edge 58 ismaintained by adjusting vertically-oriented linear slide 168 andhorizontally oriented linear slide 174.

Measuring implement 160 includes a proving ring 182 is attached to anequalization arm 183 that extends between and is attached to the distalends of first and second horizontal slide members 176 and 177. As seenin FIG. 6, proving ring 182 includes a ring portion 184 and first andsecond bosses 186 and 187 integrally formed with ring portion 184. Firstand second bosses 186 and 187 extend outwardly from opposite sides ofring portion 184. First boss 186 is attached along the center of theequalization arm 183, and second boss 187 is attached to an L-shapedbracket 188 supporting contacting element 180.

As shown in FIG. 6, L-shaped bracket 188 preferably includes first andsecond members 188A and 188B. Second boss 187 is attached to firstmember 188A, and the contacting element 180 (i.e. a sphere, ball,cylinder) is attached to second member 188B using a pin (not shown).Contacting element 180 can be provided with bearings such that it iscapable of rotation relative to the pin.

With reference again to FIGS. 6 and 7, a sled 192 is attached to supportplate 163 to ensure proper positioning of the continuous product 10′ orboards 10. To that end, because matrix 11 travels in the machinedirection (from the bottom to the top of FIG. 6), sled 192 includes anon-slanted portion 194, a slanted portion 196, and an optionallyslanted portion 197. A vertically-oriented slot 198 is provided throughnon-slanted portion 194 for receiving a portion of contacting element180. During operation, slanted portion 196 funnels continuous product10′ or board 10 in position along non-slanted portion 194.

Sled 192 is attached to stationary table 162 via first and secondsupport brackets 200 and 201 which are respectively attached to firstand second air cylinders 202 and 203. First and second air cylinders 202and 203 are capable of reciprocally moving first and second brackets 202and 203 to properly position sled 192 relative to matrix 11 orcontacting element 180. Air cylinders 202 and 203 can be attached to orbe configured to move in unison with horizontally-oriented slide 174 soas to maintain a constant position, in the cross-machine direction, ofthe contacting element 180 relative to sled 192. Otherwise, positionsensors, in addition to those described below, may be required tomaintain the degree to which contacting element 180 (i.e. sphere, ball,cylinder, or the like) is pressed into foam matrix 11.

Sled 192 can be provided with first and second photo-electric cells 204and 205 to determine the position of matrix 11 relative to contactingelement 180. First and second photo-electric cells 204 and 205 can berespectively positioned along the top edge of non-slanted portion 194,and are interconnected with a computer microprocessor or electronicprocessor (not shown). According to the signals received from first andsecond electric cells 204 and 205, the computer microprocessor (which isalso connected to the self-adjusting assembly 166) alters the positionof contacting element 180 relative the trimmed edge 58 by actuatingvertically-oriented linear slide 168 and horizontally-oriented linearslide 174. For example, actuation of vertically-oriented linear slide168 effects the position of contacting element 180 alongvertically-oriented slot 198 and trimmed edge 58, and actuation ofhorizontally-oriented linear slide 174 effects the position of thecontacting element 180 in the cross-machine direction relative totrimmed edge 58.

Ideally, the computer microprocessor controls actuation ofself-adjusting assembly 166 to position the contacting element 180 inthe vertical center of trimmed edge 58. When contacting element 180 isproperly positioned relative to trimmed edge 58, contacting element 180creates an impression in foam matrix 11. In doing so, foam matrix 11resultantly exerts a force against contacting element 180. The footprintor area of the impression is constantly maintained by the properpositioning of contacting element 180 (i.e. sphere, ball, cylinder, orthe like) and sled 92.

Operation of proving ring 182 is afforded by the rigid attachment offirst boss 186 to the equalization arm, and of second boss 187 toL-shaped bracket 188 (which supports contacting element 180). Forexample, the force exerted by foam matrix 11 on contacting element 180is imparted through L-shaped bracket 188, and second boss 187 to thering portion 184 of proving ring 182. Ring portion 184 deforms accordingto the magnitude of the imparted force. To accurately measure the amountof the imparted force, ring portion 184, as seen in FIG. 6, includes anLVDT 206 and an armature 207.

LVDT 206 is a cylinder (or tube) affixed on the interior of proving ring182 adjacent second boss 187. Armature 207 is adapted to partially fitwithin LVDT 206, and is affixed to the interior of proving ring 182adjacent first boss 186. To generate a signal proportion to the impartedforce, a voltage is induced in LVDT 206, and the magnitude of theinduced voltage varies depending on the displacement of armature 207inside LVDT 206. For example, armature 207 can be configured to becapable of moving 0.03″ relative to LVDT 206, and using the inducedvoltage, LVDT 206 generates a signal that is linearly proportional tothe displacement (from 0.00 to 0.03″) of armature 207 inside LVDT 206.Therefore, when proving ring 182 is deformed, armature 207 is displacedinside LVDT 206, and an appropriate signal is generated.

As discussed in accordance with edge-strength measuring device 52, thesignal generated by LVDT 206 of edge-strength measuring device 152 isrelayed to the computer microprocessor which modifies the signalaccording to the area of the footprint of contacting element 180 togenerate a pressure measurement indicating the compressive strengthalong trimmed edge 58, for example. The compressive strength measurementcan be used as quality control information to allow an operator tocontinuously monitor the manufacturing run to effect the compressivestrength along the edges of foam matrix 11 to ensure that boards 10′ aresufficiently durable as to be resistant to edge collapse.

The quality control information allows an operator to continuouslymonitor the manufacturing run to effect the desired compressive strengthalong the edges of the foam matrix. The signals generated by LVDT 142provide a feedback loop that allows the operator to adjust components ofthe manufacturing process to effect the desired compressive strengthalong the edges of the foam matrix and, thereafter, monitor whether thecompressive strength has actually been modified. Consequently, theoperator can continuously monitor and update the manufacturing processduring a manufacturing run to ensure that foam matrix 11 of the board10′ is sufficiently resistant to edge collapse.

As noted above, the process of on-line monitoring provided by thepresent invention allows operators of the continuous foam making processreal time information. With this information, the operator can makeadjustments to the process that can improve the dimensional stability ofthe insulation boards, especially along the edges. There are numerousadjustments that an operator can make. For example, the level or amountof catalyst employed or added to the process as an ingredient can beadjusted. Typically the level of catalyst is proportional to the degreeof cure. Also, the operator can alter the level or amount of the otheringredients employed to form the foam. For example, the type amount ofblowing agent can be adjusted. Still further, the operator can alter thepositioning of the mix heads above the conveyer. As those skilled in theart will appreciate, continuous processes for the manufacture ofpolyurethane or polyisocyanurate foam insulation boards employ multiplemix heads (e.g., three mix heads) that deposit the foam forming materialonto the conveyer. The positioning of the outermost mix heads (i.e.,those proximate to the side rails) can alter the formation of the foam,especially near the side rails, which can ultimately have an impact ondimensional stability. Even further, the operator can adjust thetemperature of the heaters or ovens that may be employed to cure thefoam. Once provided with real-time information as to the compressivestrength along the edges of the board, operators will be able to developseveral techniques or combinations thereof to adjust the process andthereby improve the dimensional stability (or the consistency of thedimensional stability throughout the manufacturing process) of theresultant boards.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A method for producing foam insulation board, the method comprising:forming a foam product as part of a continuous process, where said foamproduct includes at least one side edge; monitoring on-line thecompressive strength of the foam product, along said at least one sideedge; and adjusting said step of forming a foam product in view of dataobtained from said step of monitoring, where said step of forming a foamproduct includes depositing, from multiple mix heads, a foam formingmaterial onto a conveyor, and where said step of adjusting includesaltering the position of the mix heads in view of the data obtained fromsaid step of monitoring.
 2. The method of claim 1, further comprisingthe step of trimming said side edges prior to said step of monitoring.3. The method of claim 1, where said step of monitoring includesengaging the at least one side edge with a contact element.
 4. Themethod of claim 1, where the foam product includes first and second sideedges, said step of monitoring includes measuring the compressivestrength at both the first and the second side edge.
 5. The method ofclaim 1, further comprising the step of cross-cutting the foam productinto boards subsequent to said step of monitoring.
 6. The method ofclaim 1, where said step of monitoring provides information relative tothe dimensional stability of the foam product.